You ask some very good questions here. First off, I'll give you the link to Spyderco's Steel Chart and Steel Education page. It is good reading and will give you an idea as to what elements in the steels you mentioned do. Also, I'd suggest reading Joe Talmadge's Steel FAQ, as it too is a great resource.
Selecting 'the right' steel is purely subjective and depends entirely on what you intend on doing with your knife. Instead of telling you what 'the best' steel is of the one's you've mentioned, I'm going to list similar steels (in bold) next to the ones you've listed, and I'll also list what type of activity I think that steel would be good at (also in bold). YMMV.